GCN Circular #18570
Matthew Stanbro (UAH) and Charles Meegan (UAH)
report on behalf of the Fermi GBM Team:
"At 20:24:52.30 UT on 07 November 2015, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 151107B (trigger 468620696 / 151107851).
The on-ground calculated location, using the GBM trigger
data, is RA = 31.3, DEC = 45.6, with an uncertainty
of 1.7 degrees (radius, 1-sigma containment,
statistical only; there is additionally a systematic
error which we have characterized as a core-plus-tail model, with 90% of
GRBs having a 3.7 deg error and a small tail suffering a larger than 10 deg
systematic error. [Connaughton et al. 2015, ApJS, 216, 32] ).
The trigger resulted in an Autonomous Repoint Request (ARR)
by the GBM Flight Software owing to the high peak flux
of the GRB. This ARR was accepted and the spacecraft slewed to the GBM in-flight
location. The initial angle from the Fermi LAT boresight to
the GBM ground location is 40 degrees.
The GBM light curve consists of 2 separate episodes
with a duration (T90) of about 139 s (50-300 keV).
The time-averaged spectrum from T0+2 s to T0+137 s is
best fit by a power law function with an exponential
high-energy cutoff. The power law index is -1.20 +/- 0.02 and
the cutoff energy, parameterized as Epeak, is 347 +/- 25 keV
The event fluence (10-1000 keV) in this time interval is
(3.11 +/- 0.07)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+8.13 s in the 10-1000 keV band
is 10.9 +/- 0.2 ph/s/cm^2.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."

GCN Circular #18574
S.Karpov, G.Beskin (SAO RAS and Kazan Federal University, Russia), S.Bondar,
E.Ivanov, E.Katkova, A.Perkov, N.Orekhova (OJS RPC PSI, Russia), A.Biryukov
(SAI MSU and Kazan Federal University, Russia), V.Sasyuk (Kazan Federal
University, Russia)
The localization of Fermi GBM trigger 468620696 / GRB 151107B (Stanbro et al,
GCN Circ. 18570) has been observed by Mini-MegaTORTORA nine-channel wide-field
monitoring system (located at Special Astrophysical Observatory near Russian
6-m telescope and belonging to Kazan Federal University) before, during and
after the trigger time at 2015-11-07 20:24:52.30 UT. The whole final 1-sigma
localization box (as well as 6 more degrees around it) has been covered since
20:19:23 UT (T-329.3 s) and until 20:25:18 UT (T+25.7 s, thus covering the
brightest part of first gamma-ray peak) with temporal resolution of 0.1 s in
white light. Dedicated real-time transient detection pipeline did not detect
any events longer than 0.3 s and brighter than approximately V=10.5 mag. Visual
inspection of co-added images with 10 s effective exposure (summation of 100
consecutive frames each) has not revealed any variable source down to V=12.0
mag during that interval.
At 20:25:18 UT the system initiated a repointing following the initially
distributed GBM coordinates, and since 20:25:55 UT (T+62.7 s, during the
continuing gamma-ray activity) till 20:35:59 UT (T+666.7 s) acquired 20x9 deep
images with 30 s exposures in white light in a 30x30 degree field of view
centered on RA=24.1 Dec=44.8. The whole final 1-sigma localization was still
inside the field of view. Quick-look analysis of the acquired data has not
revealed any variable object down to roughly V=13.5 mag over that time interval.
The analysis is ongoing.